Strontium sealed source

ABSTRACT

The disclosure pertains to a strontium-90 sealed radiological or radioactive source, such as may be used with treatment of the eye or other medical or industrial processes. The sealed radiological source includes a radiological insert within an encapsulation. The encapsulation may include increased shielding in the center thereof.

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 15/571,310, filed on Nov. 2, 2017, now U.S. Pat.No. 10,714,226, which claims priority of PCT/US2016/022437, filed Mar.15, 2016, which claims priority under 35 U.S.C. 119(e) of U.S.provisional application Ser. No. 62/158,091, filed on May 7, 2015, thecontents of all of which is hereby incorporated by reference in itsentirety and for all purposes.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The disclosure pertains to a strontium-90 scaled source, such as may beused with treatment of the eye or other medical, brachytherapeutic orindustrial processes. In particular, a relatively constant absorbed doserate is sought throughout a target volume of tissue of therapeuticinterest that is to be treated with radiation (hereinafter referred toas “a flat radiation profile”).

Description of the Prior Art

The prior art of radiological or radioactive sources of various typesfor medical, industrial and other processes is well-developed. Forexample, U.S. Pat. No. 8,430,804, entitled “Methods and Devices forMinimally-Invasive Extraocular Delivery of Radiation to the PosteriorPortion of the Eye”, issued on Apr. 30, 2013 to Brigatti et al., andassigned on its face to Salutaris Medical Devices, Inc., discloses anapplicator for minimally-invasive delivery of beta radiation from aradionuclide brachytherapy source to the posterior portion of the eye.In particular, this is adapted for the treatment of various diseases ofthe eye, such as, but not limited to, wet age-related maculardegeneration. Other prior art includes U.S. Pat. No. 9,873,001 entitled“Methods and Devices for Minimally-Invasive Delivery of Radiation to theEye”, issued on Jan. 23, 2018 to Lutz et al. and assigned on its face toSalutaris Medical Devices, Inc.; PCT/US2014/056135 entitled “RadiationSystem with Emanating Source Surrounding an Internal AttenuationComponent”, filed on Mar. 18, 2016; U.S. Pat. No. 7,070,554 entitled“Brachytherapy Devices and Methods of Using Them”, issued on Jul. 4,2006 to White et al., and assigned on its face to TheragenicsCorporation and U.S. Pat. No. 6,413,881, entitled “OphthalmicBrachytherapy Device”, issued on Sep. 3, 2002 to Finger.

While this prior art is well-developed and suited for its intendedpurposes, further improvements are sought in the radioactive sourcesused in the disclosed devices. In particular, a collimated distributionof radiation, rather than an isotropic (spherical “4π”) distribution ofradiation, would allow a radiological source to direct radiation at thetissues under treatment, while reducing radiation directed atsurrounding tissues which are not under treatment and also whilepreventing excessive radiation to be directed to the tissues undertreatment in the center of the emitted radiation beam.

OBJECTS AND SUMMARY OF THE DISCLOSURE

It is therefore an object of the present disclosure to provideimprovements in the radiological sources used in brachytherapy and inother medical or industrial applications. In particular, it is an objectof the present disclosure to provide improved radiological sources forknown applicators for treatment of diseases of the eye, including, butnot limited to, wet age-related macular degeneration. These radiologicalsources are intended to concentrate the radiation more uniformly on thediseased tissue, rather than using isotropic radiation which wouldexpose more of the surrounding healthy tissue to unnecessary radiationand could overexpose tissue under treatment at the center of theradiation beam.

This and other objects are attained by providing a beta radiologicalsource, typically containing strontium-90, wherein the radiologicalinsert has increased radioactivity around its periphery and lessradioactivity at its center. This may be achieved by a toroidal orannular shape, (such as a donut-type shape with a hole or aperture inthe middle) or with the central portion of a disk having reducedthickness or reduced radioactivity content. This may further be achievedby a minus lens meniscus shape wherein the lower concave surface has ashorter radius of curvature than the upper concave surface, therebyresulting in a raised thinner portion and a lower thicker peripheralportion. This is further achieved by providing an encapsulation withincreased shielding in the center of the face from which the therapeuticradiation is emitted, thereby substantially attenuating the radiationemitted from the central portion of a source. It is further possible touse a separate denser attenuating disk in front of the activity, eitheron the inside or outside of the encapsulation. Material in theattenuating disk may include, but is not limited to, silver, copper,lead, tungsten, gold and/or iridium.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the disclosure will become apparentfrom the following description and from the accompanying drawings,wherein:

FIG. 1 is a cross-sectional view of an embodiment of a radiologicalsource of the present disclosure.

FIG. 2 is an illustration relating to the radiation dose profilegenerated by the radiological source of FIG. 1.

FIGS. 3A-3F illustrates various further embodiments of the radiologicalsource of the present disclosure.

FIG. 4 illustrates a placement of the radiological source with respectto a human eyeball during medical treatment.

FIG. 5 illustrates a portion of FIG. 4 in greater detail.

FIG. 6 illustrates a still further embodiment of the radiological sourceof the present disclosure, including a minus-lens meniscus shape.

FIGS. 7A and 7B illustrate a still further embodiment of theradiological source of the present disclosure, wherein multiple elementsare placed in a quasi-toroidal shape in one or two layers.

FIGS. 8A, 8B and 8C illustrate yet still further embodiments of theradiological source of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings in detail wherein like numerals refer tolike elements throughout the several views, one sees that FIG. 1illustrates a cross-sectional view of an embodiment of the radiologicalsource 100. The radiological source 100 is substantially rotationallysymmetric, including cylindrical, annular and toroidal shapes. A capsulebody 300, typically made of titanium or stainless steel, includes alower floor 302 with a central plateau 304 thereby forming a toroidalchannel 306 between the central plateau 304 (thereby increasing the betashielding in central portions of the lower floor 302) and the outercylindrical wall 308 of the capsule body 300. The upper edge of outercylindrical wall 308 forms a circular opening for receiving outer lid310 which is generally cylindrical but includes a chambered lowercircular edge 312 and further includes a central cylindrical blindopening 314 for receiving telescoping inner lid 316, and typicallyforming a tight friction or interference fit therebetween in order totightly position the radiological insert 318 within the capsule body300. Outer lid 310, which is typically made of titanium or stainlesssteel and illustrated with an interior circumferential toroidal ridge327, is typically welded to capsule body 300, using conventionalstandards of the industry. Strontium-90 radiological insert 318 (similarto insert 130 in previous embodiments) includes an upper circular ordisk-shaped portion 320 which is engaged between a lower edge oftelescoping inner lid 316 and central plateau 304 of capsule body 300.This configuration is intended to reduce rattling of the strontium-90radiological insert 318. The upper surface of strontium-90 radiologicalinsert 318 includes a convex central region 325. This convex centralregion 325 is intended to reinforce the structure and avoid or minimizewarping and possible delamination during production. Strontium-90radiological insert 318 further includes a downwardly extendingcircumferential toroidal portion 323 which extends into toroidal channel306 of capsule body 300.

The toroidal shape of the strontium-90 radiological insert 318, with itsthickened periphery, leads to increased radiation emission around theperiphery and a reduced radiation output within the center. This, incombination with the increased beta shielding in the central area ofcentral plateau 304, results in a flat beam profile, achieving a moreconstant absorbed dose rate throughout a target volume of tissue oftherapeutic interest that is located in front of the source asillustrated in FIG. 2, wherein typical values are given for aradiological source 100 of a diameter of 4.05 millimeters and a maximumheight of 1.75 millimeters. In the given example, a intended therapeuticvolume 400 with a diameter of 3.0 millimeters and a depth of 1.438 to2.196 millimeters (with a mean depth to target of 1.817 millimeters fromthe lower surface of the radiological source 100) in a first case or adepth of 1.353 to 2.111 millimeters (with a mean depth to target of1.752 millimeters from the lower surface of the radiological source 100)in a second case. A radius of 11.50 millimeters is typical for thesclera 2002 (outer covering) of a human eyeball 2000 (see also FIGS. 4and 5). Those skilled in the art, after review or this disclosure, willunderstand that different structural parameters will result in differentradiation distributions, as may be required by the specific application.

It is noted that the strontium-90 beta radiation insert 130 may be madeof various materials, such as a strontium ceramic, strontium glass, or acollection of tightly packed ceramic beads (of various possible shapes)or a refractory-metal composite. Refractory ceramics and glassescontaining Strontium-90 can be made from a wide variety of materials incombination, such as those containing metal oxides of aluminum, silicon,zirconium, titanium, magnesium, calcium amongst others. It is envisionedthat other additional materials may be selected from, but not limitedto, such strontium-90 compounds as SrF₂, Sr₂P₂O₇, SrTiO₃, SrO, Sr₂TiO₄,SrZrO₃, SrCO₃, Sr(NbO₃)₂, SrSiO₃, 3SrO.Al₂O₃, SrSO₄, SrB₆, SrS, SrBr₂,SrC₂, SrCl₂, SrI₂ and SrWO₄. Additionally, beta emitters based onmaterials other than strontium-90 may also be compatible with thisdisclosure. Such beta emitters may include Copper-66, Lead-209,Praseodymium-145, Tellurium-127, Tin-121, Nickel-66, Yttrium-90,Bismuth-210, Erbium-169, Praseodymium-143, Phosphorus-32, Phosphorus-33,Strontium-89, Yttrium-91, Tungsten-188, Sulfur-35, Tin-123, Calcium-45,Berkelium-249, Ruthenium-106, Thulium-171, Promethium-147, Krypton-85,Hydrogen-3, Cadmium-113m, Plutonium-241, Strontium-90, Argon-42,Samarium-151, Nickel-63, Silicon-32, Argon-39, Carbon-14, Technetium-99,Selenium-79, Beryllium-10, Cesium-135, Palladium-107, Rhenium-187,Indium-115 and Cadmium-113. In particular, after commercial andtechnical considerations (e.g., energy level and half-life), thefollowing are of particular interest—Strontium-90/Yttrium-90,Strontium-89, Phosphorus-32, Tin-123 and Yttrium-91.

FIGS. 3A through 3F illustrate six further design embodiments ofradiological source 100 of the present disclosure. The radiologicalsource 100 of FIG. 3A is very similar to FIG. 1 and includes capsulebody 300 includes a lower floor 302, the interior wall of the lowerfloor 302 including a central plateau 304 on the interior thereofthereby forming a toroidal channel 306 between the central plateau 304and the outer cylindrical wall 308 of the capsule body 300. The upperedge of outer cylindrical wall 308 forms a circular opening forreceiving outer lid 310 which is generally cylindrical. Outer lid 310 istypically welded to capsule body 300, using conventional standards ofthe industry. Strontium-90 radiological insert 318 is toroidally shapedby rotating a rectangular cross-section about the central axis therebyresulting in a central passageway 319. Toroidally-shaped radiologicalinsert 318 is positioned above the toroidal channel 306, and supportedby central plateau 304 and shoulder 308A, 308B formed within an interiorof outer cylindrical wall 308. A cylindrical disk-shaped spacer 320,typically made of titanium or stainless steel, is positioned between theradiological insert 318 and the lower surface of the outer lid 310.Additionally, a cylindrical shielding insert 322, typically made fromtitanium or stainless steel, inserted within the central aperture 319.The shape of the strontium-90 radiological insert 318 leads to increasedradiation output around the periphery, with a reduced radiation outputwithin the central aperture 319. This, in combination with the increasedshielding in the central area of central plateau 304 and the cylindricalshielding insert 322, results in a flat beam profile, achieving a moreconstant absorbed dose rate throughout a target volume of tissue oftherapeutic interest that is located in front of the source (i.e.,anisotropic) characteristic of the resulting beta radiation.

The embodiment of radiological source 100 in FIG. 3B is similar to thatof FIG. 3A. The interior wall of lower floor 302 is generally planarwithout the central plateau of FIG. 3A. The toroidal-shaped strontium-90radiological insert 318 is secured to cylindrical disk-shaped spacer 320by a low-melting glass bond 321 or similar configuration. Cylindricalshielding insert 322 extends from spacer 320 to the inner wall of lowerfloor 302, thereby resulting in a configuration with a toroidal-shapedvoid 306′ below the toroidal-shaped strontium-90 radiological insert318. The shape of the strontium-90 radiological insert 318 leads to anincreased radiation source around the periphery, with a removal of asource of radiation within the central aperture 319. This, incombination with the increased shielding of the cylindrical shieldinginsert 322, results in a flat beam profile, achieving a more constantabsorbed dose rate throughout a target volume of tissue of therapeuticinterest that is located in front of the source).

The embodiment of radiological source 100 in FIG. 3C is similar to thatof FIG. 3A. The toroidal-shaped strontium-90 radiological insert 318includes a central cylindrical disk portion 318A and further includesupper and lower toroidal portions 318B, 318C, respectively, extendingaround the circumference thereof. Additionally, spacer 320 furtherincludes a downwardly extending cylindrical skirt 320A which outwardlyabuts the circumference of toroidal-shaped strontium-90 radiologicalinsert 318. Spacer 320 further includes a central cylindrical aperture320B which receives a variation of shielding insert 322, furtherincluding a downwardly extending frusto-conical portion 322A forengaging against central cylindrical disk portion 318A of strontium-90radiological insert 318 and being positioned within the upper toroidalportion 318B of strontium-90 radiological insert 318. This configurationengages the central cylindrical disk portion 318A between the downwardlyextending frusto-conical portion 322A of shielding insert 322 andcentral plateau 304. Similar to the embodiment of FIG. 3B, atoroidal-shaped void 306′ is formed between the lower toroidal portion318C of strontium-90 radiological insert 318 and the inner wall of floor302. The shape of the strontium-90 radiological insert 318 leads to anincreased radiation source around the periphery, with a reduction in theradiation from cylindrical disk portion 318A. This, in combination withthe increased shielding of the central plateau 304, results in a flatbeam profile, achieving a more constant absorbed dose rate throughout atarget volume of tissue of therapeutic interest that is located in frontof the source).

The embodiment of FIG. 3D is similar to that of FIG. 3B. However, theinterior of cylindrical wall 308 includes shoulders 308A, 308B forsupporting the toroidal-shaped strontium-90 radiological insert 318above the toroidal channel 306. This may eliminate the need for the lowmelting glass bond 321 or similar configuration to affix thetoroidal-shaped strontium-90 radiological insert 318 to the spacer 320.The shape of the strontium-90 radiological insert 318 leads to anincreased radiation source around the periphery, with a removal of asource of radiation within the central aperture 319. This, incombination with the increased shielding of the cylindrical shieldinginsert 322, results in a flat beam profile, achieving a more constantabsorbed dose rate throughout a target volume of tissue of therapeuticinterest that is located in front of the source).

The embodiment of FIG. 3E is similar to that of FIG. 3C. Thetoroidal-shaped strontium-90 radiological insert 318 includes a centralcylindrical disk portion 318A and further includes a lower toroidalportion 318C extending around the circumference thereof. The lack of aupper toroidal portion allows the spacer 320 to be simplified to acylindrical disk shape. The shape of the strontium-90 radiologicalinsert 318 leads to an increased radiation source around the periphery,with a reduction in the radiation from cylindrical disk portion 318A.This, in combination with the increased shielding of the central plateau304, results in a flat beam profile, achieving a more constant absorbeddose rate throughout a target volume of tissue of therapeutic interestthat is located in front of the source).

The embodiment of FIG. 3F is similar to that of FIG. 3E. Thestrontium-90 radiological insert 318 is simplified to a disk shape,rather than a toroidal shape. Additionally, spacer 320 further includesa downwardly extending cylindrical skirt 320A which outwardly abuts thecircumference of toroidal-shaped strontium-90 radiological insert 318.The strontium-90 radiological insert 318 is secured to cylindricaldisk-shaped spacer 320 by a low-melting glass bond 321 so as to besuspended above central plateau 304 and toroidal channel 306. It isenvisioned that this embodiment could further have the strontium-90radiological insert 318 contacting and being supported, at least inpart, by central plateau 304.

The embodiment of FIG. 6 is a Strontium-90 radiological insert 500 witha (rotationally symmetric) minus-lens meniscus shape wherein there aretwo different curvatures on the upper and lower surfaces 502, 504. Theupper surface 502 (or “rear”) is convex, the lower surface 504 (or“face”) is concave 504 and the radiological insert 500 is thinner at itscenter 510 (i.e., along the rotational axis) than at its edges 512, 514.Typically, this minus-lens meniscus shape may be implemented by having ashorter radius of curvature for the lower surface 504 than for the uppersurface 502. While not shown, this radiological insert 500 willtypically be encased by an encapsulation or capsule body 300 similar tothat shown in FIGS. 3A-3F, possibly with increased shielding in acentral portion thereof (that is, below the center 510) in order toachieve a flatter radiation profile. This meniscus configuration may beconsidered, from a mathematical point of view, to be mid-way between acylindrical or flat disk and a toroidal “donut-shaped” configuration.The configuration may be termed “meniscus,” “biconcave,” or “planarconcave.”

The embodiment of FIG. 7A illustrates a Strontium-90 radiological insert600 comprising a ring of disk-like sub-elements of Strontium-90 602arranged in a quasi-toroidal shape. Similarly, the embodiment of FIG. 7Billustrates a Strontium-90 radiological insert 600 comprising a firstring of disk-like sub-elements of Strontium-90 602 arranged in aquasi-toroidal shape, with second ring of disk-like sub-elements ofStrontium-90 604, rotationally offset by the radius or one half of theexpanse of one disk from the first ring, and axially offset, typicallyby the thickness of the sub-elements 602, 604. The first and secondrings are adjacent to each other and share a common rotational axis 606.The embodiments of FIGS. 7A and 7B further include a sealedencapsulation.

The embodiments of FIGS. 8A, 8B and 8C include a metallic, ceramic orsimilar dish 700 into which fused Sr-90 glass 702 is melted and bonded.The Sr-90 glass 702, in a viscous state, is poured into the dish in aninverted position from that shown in FIGS. 8A, 8B and 8C so as to form ameniscus 704 (the illustrated concave surface). In order to increase theamount of Sr-90 glass at the peripheral portions of the dish 700,toroidal troughs 706 may be formed such as is illustrated in FIGS. 8Aand 8B. These embodiments of FIGS. 8A, 8B and 8C further include asealed encapsulation.

Further alternatives to the present disclosure include fixation of theactive insert using glass, such as glass pre-melted into a stainlesssteel insert, glass powder co-compacted with a ceramic and glass powdermixed with a ceramic and then compacted. Additionally, alternativesinclude fixation of the active insert using mechanical methods such assoft materials such as copper, silver, aluminum, etc. or the use ofsprings of various types (wave, conical, folded disk, etc.). Furtheralternatives include active insert centering features to preventpositional errors such as tapered ceramic disks or a disk with anaperture or protrusion which interfaces with the capsule lid.

Similarly, the various embodiments of the radiological sources whichinclude a cavity could be implemented by filling the cavity withradioactive microspheres. Such shapes would be defined by the shape ofthe cavity inside the source, while the microspheres could beimmobilized using washers, spaces or similar devices during assembly.Further alternative embodiments include radioactive microspheres whichare bonded using a fused glass/enamel bonding material to an insert(e.g., a metal or ceramic support) to immobilize the microspheres anddefine their shape.

In a further aspect of this disclosure, aqueous ammonia solution (NH₄OH)is added to a mixed aqueous solution containing dissolved radioactivestrontium nitrate ⁹⁰Sr(NO₃)₂ and dissolved silver nitrate (AgNO₃) (goldor copper may be substituted for silver in some applications, mixturesof silver, gold or copper may also be used) and a mixed precipitate canform of sparingly soluble silver hydroxide AgOH (some of which mayconvert to silver oxide Ag₂O plus water in situ) and strontium hydroxide⁹⁰Sr(OH)₂. Soluble ammonium nitrate NH₄NO₃ remains in solution. Excessammonium hydroxide produces a water-soluble ammoniacal silver complex[Ag(NH₃)₂OH] while the strontium hydroxide remains insoluble. Thesolution and/or the mixed precipitates can be evaporated so that allsolids co-precipitate or crystalize out of solution to produce anintimate mixture. These solids are baked dry so that the ammoniumnitrate decomposes and sublimes (above 250° Centigrade) leavingsubstantially nothing behind, silver hydroxide decomposes to silveroxide then further decomposes to silver metal and the strontiumhydroxide decomposes to strontium oxide. What is left is an intimatemixture of silver metal and strontium oxide (⁹⁰SrO+Ag). Because silveris a soft semi-precious metal, such an intimate mixture of silver andradioactive strontium oxide can be mechanically and/or thermally formedinto thin toroidal insert shapes by processes such as pressing, forging,rolling, extrusion and/or sintering.

Silver hydroxide or silver oxide can be prepared and pressed into a diskshape (toroidal or flat) at a pressure sufficient to bind the particlestogether to produce a handleable green-state disk (an organic orinorganic binder can be added if needed) but at a pressure that is lowenough to leave porosity or microporosity within the disk. Aqueousstrontium nitrate ⁹⁰Sr(NO₃)₂ can then be soaked into the disk and thendried down to achieve intimate mixing. The dried disk can be sintered toproduce a fully dense cermet containing strontium oxide embedded orimmobilized within the matrix formed of copper oxide, silver oxide,copper hydroxide, silver hydroxide, gold hydroxide (i.e., auric acid) ormixtures thereof. The proportions of strontium and silver (or gold,copper or mixtures thereof) can be varied, resulting in differentmechanical properties. Less strontium produces more ductility but athicker more-attenuating disk. The typical range of composition can be2-50 mol percent of strontium oxide in silver, gold or copper,preferably 5-40 mol percent, more preferably 10-30 mol percent. Cermetdisks can be re-pressed or otherwise mechanically or thermally treatedafter sintering to further densify or remold the shape of the disks.

In a further aspect of this disclosure, Strontium-90 compounds areincorporated or mixed with aluminum to make a composite material. Thismay be performed by a method of incorporating Strontium-90 into aluminumby mixing or blending strontium fluoride (⁹⁰SrF₂) powder with aluminumpowder, compressing the mixture into a billet, then heating it to about10° Centigrade below the melting point of aluminum (660.3° Centigrade)before extruding the billet through an aperture in a metal collar toproduce a wire of ⁹⁰SrF₂+Al. The resulting material can be formed into atoroidal disk or similar configuration as described in this disclosure.

Strontium fluoride is a stable material. It melts at 1477° Centigradeand is insoluble in water (K_(sp) value is approximately 2.0×10⁻¹⁰ at25° Centigrade). It can be made from commercially available strontiumnitrate ⁹⁰Sr(NO₃)₂ by adding soluble ammonium fluoride to a strontiumnitrate solution, precipitating insoluble strontium fluoride (⁹⁰SrF₂)and mixing/blending the dried salt with aluminum powder before pressingthe mixture/blend into a disk. Useful ratios of ⁹⁰SrF₂ to Al couldtypically be in the range 5-50% of ⁹⁰SrF₂, preferably 10-30% (byweight). The resulting material can be formed into a toroidal disk orsimilar configuration as described in this disclosure.

Alternatively, an aqueous solution of ⁹⁰Sr(NO₃)₂ could be absorbed intoa disk made of porous or microporous aluminum and then dried down andbaked above the decomposition temperature of ⁹⁰Sr(NO₃)₂ of 570°Centigrade but below the melting point of aluminum 660.3° Centigrade ina non-oxidizing atmosphere, to convert the strontium nitrate intostrontium oxide. This could be achieved in a vacuum oven or under aninert gas such as argon or a reducing atmosphere such as anargon-hydrogen mixture. Other soluble forms of Strontium-90 could beabsorbed and baked in similar ways. The resulting material can be formedinto a toroidal disk or similar configuration as described in thisdisclosure.

Thus the several aforementioned objects and advantages are mosteffectively attained. Although preferred embodiments of the inventionhave been disclosed and described in detail herein, it should beunderstood that this invention is in no sense limited thereby.

What is claimed is:
 1. A radiological insert with an upper convex surface and a lower concave surface, wherein a radius of curvature of the lower concave surface is shorter than a radius of curvature of the upper convex surface; wherein the radiological insert is rotationally symmetric with a minus-lens meniscus shape; wherein a center of the radiological insert is thinner than edges of the radiological insert; and wherein the radiological insert is a beta-emitter.
 2. The radiological insert of claim 1 wherein the radiological insert includes strontium-90, wherein the strontium-90 is contained in a material or compound selected from the group consisting of a strontium ceramic, a strontium glass, SrF₂, Sr₂P₂O₇, SrTiO₃, SrO, Sr₂TiO₄, SrZrO₃, SrCO₃, Sr(NbO₃)₂, SrSiO₃, 3SrO.Al₂O₃, SrSO₄, SrB₆, SrS, SrBr2, SrC₂, SrCl₂, SrI₂ and SrWO₄.
 3. The radiological insert of claim 1 wherein the radiological insert includes a beta source, contained in a material or compound, wherein the beta source is selected from the group consisting of Copper-66, Lead-209, Praseodymium-145, Tellurium-127, Tin-121, Nickel-66, Yttrium-90, Bismuth-210, Erbium-169, Praseodymium-143, Phosphorus-32, Phosphorus-33, Strontium-89, Yttrium-91, Tungsten-188, Sulfur-35, Tin-123, Calcium-45, Berkelium-249, Ruthenium-106, Thulium-171, Promethium-147, Krypton-85, Hydrogen-3, Cadmium-113m, Plutonium-241, Strontium-90, Argon-42, Samarium-151, Nickel-63, Silicon-32, Argon-39, Carbon-14, Technetium-99, Selenium-79, Beryllium-10, Cesium-135, Palladium-107, Rhenium-187, Indium-115 and Cadmium-113. 